scholarly journals Crack Width and Load-Carrying Capacity of RC Elements Strengthened with FRP

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Justas Slaitas ◽  
Mykolas Daugevičius ◽  
Juozas Valivonis ◽  
Tatjana Grigorjeva
Keyword(s):  
Crack Propagation ◽  
Carrying Capacity ◽  
Crack Width ◽  
Crack Depth ◽  
Experimental Program ◽  
Mechanics Of Solids ◽  
Crack Model ◽  
Load Carrying Capacity ◽  
Rc Structures ◽  
Load Carrying

The present study focuses on a prediction of crack width and load-carrying capacity of flexural reinforced concrete (RC) elements strengthened with fibre-reinforced polymer (FRP) reinforcements. Most studies on cracking phenomena of FRP-strengthened RC structures are directed to empirical corrections of crack-spacing formula given by design norms. Contrary to the design norms, a crack model presented in this paper is based on fracture mechanics of solids and is applied for direct calculation of flexural crack parameters. At the ultimate stage of crack propagation, the load-carrying capacity of the element is achieved; therefore, it is assumed that the load-carrying capacity can be estimated according to the ultimate crack depth (directly measuring concrete’s compressive zone height). An experimental program is presented to verify the accuracy of the proposed model, taking into account anchorage and initial strain effects. The proposed analytical crack model can be used for more precise predictions of flexural crack propagation and load-carrying capacity.

Flexural strengthening of pre-cracked RC slabs with prestressed NSM CFRP laminates and evaluation of strain loss

2021 ◽  
pp. 136943322110105
Author(s):  
M.R. Mostakhdemin Hosseini ◽  
Salvador J.E. Dias ◽  
Joaquim A.O. Barros
Keyword(s):  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Transfer Length ◽  
Rc Structures ◽  
Cracked Concrete ◽  
Flexural Strengthening ◽  
Cfrp Laminates ◽  
Load Carrying ◽  
Rc Slabs

The strengthening intervention of RC structures often involves already cracked concrete. To evaluate the effect of the level of damage prior to the strengthening (pre-cracks) on the behavior of the flexurally strengthened RC slabs with prestressed NSM CFRP laminates, an experimental research was carried out. Two pre-cracking levels of damage were analyzed and, for each one, three levels of prestress were tested (0%, 20% and 40%). The obtained results showed that the strengthening of damaged RC slabs with prestressed NSM CFRP laminates results in a significant increase on the load carrying capacity at serviceability limit states. Pre-cracked RC slabs strengthened with prestressed NSM CFRP laminates presented a load carrying capacity almost similar to the corresponding uncracked strengthened slabs. To determine the effective prestress level in CFRP laminates, the variation of strain over the length of the CFRP and over time was experimentally recorded. The prestress transfer length was also evaluated. The experimental results revealed that the transfer length of CFRP laminates was less than 150 mm, and the maximum value of strain loss out of transfer length (around 14%) was measured close to the cracked section of the damaged RC slabs. Significant part of strain loss in CFRP laminates occurred during 24 h after releasing the prestress load.

AN IMPROVED ANALYTICAL METHOD FOR RESTRAINED RC STRUCTURES SUBJECTED TO STATIC AND DYNAMIC LOADS

2013 ◽  
Vol 14 (01) ◽  
pp. 1350052 ◽  
Author(s):  
LI CHEN ◽  
QIN FANG ◽  
ZHIKUN GUO ◽  
JINCHUN LIU
Keyword(s):  
Test Data ◽  
Carrying Capacity ◽  
Analytical Method ◽  
Action Theory ◽  
Reinforcement Ratio ◽  
Dynamic Resistance ◽  
Load Carrying Capacity ◽  
Membrane Action ◽  
Rc Structures ◽  
Load Carrying

Once a RC structure is laterally restrained, both the static and dynamic load resistances will be enhanced due to the membrane action. Despite this known advantage, the apparent lack of systemic and efficient methods of analysis poses a drawback in the design and assessment of blast-resistant RC structures. First, a simplified membrane action theory was presented by modifying the maximum membrane force design method (MMFM) for predicting the total static resistance-deflection curves of restrained beam-slab RC structures. Second, a series of constrained beams were tested to validate the new theory, for which better agreement was observed between the test data, the results predicted by the proposed theory and those by MMFM. The results show that the static load carrying capacity and membrane force increase with increasing restraint stiffness, and the smaller the reinforcement ratio is, the larger the load carrying capacity increases. Third, based on the improved compressive static membrane action theory, a new analytical method was developed to investigate the dynamic responses of restrained RC structures subjected to blast loads, using an equivalent single degree of freedom system that combines the three-parameter elasto-viscoplastic rate-sensitive material model with the proposed static theory. Good agreement is observed between the test data and the analytical results. Finally, it is demonstrated that the dynamic resistance capacity increases with increasing load rate and restraint stiffness and with decreasing tensile reinforcement ratio, but the larger the dynamic resistance is, the larger the plastic deformation of the structure.

Investigation on the Post-Ultimate Strength Behaviour of Damaged Stiffened Plate of Ship Structure

2016 ◽  
Author(s):  
Weijun Xu ◽  
Minjie Yuan ◽  
Xiaotian Wang
Keyword(s):  
Ultimate Strength ◽  
Carrying Capacity ◽  
Crack Depth ◽  
Plate Thickness ◽  
Longitudinal Crack ◽  
Load Carrying Capacity ◽  
Stiffened Plate ◽  
Ship Structure ◽  
Plate Length ◽  
Load Carrying

Post-ultimate strength behaviour of ship structure can directly reflect its changing tendency of load carrying capacity. When the external load exerted on the ship structure exceeds the ultimate strength, sharply reduction of load carrying capacity will occur, especially for the damaged ship structure induced from grounding or collision. This paper focuses on the investigation on the post-ultimate strength behaviour of damaged stiffened plate of ship structure by using FEM, a series of stiffened plate modeling with different kinds of cracks are constructed. The parameters of crack includes length, width, depth, plate thickness and distribution direction. The post-ultimate strength behaviour of stiffened plate with cracks and intact ones are compared. Conclusion can be drawn as follows: (1) crack can induce the reduction of ultimate strength of stiffened plate, meanwhile, the stiffness and its load carrying capacity decrease accordingly. (2) in terms of stiffened thin plate, length of crack has a significant influence on the post-ultimate strength behaviour, the width of the crack has a huge influence on ultimate strength while the depth of crack has little influence; in terms of stiffened thick plate, the influence of crack depth on the post-ultimate strength behaviour becomes obvious. The width of the crack influence the post-ultimate strength behaviour a lot. (3) compare to the transverse crack, the influence of longitudinal crack on the post-ultimate strength behaviour is not obvious.

scholarly journals Experimental Study on RC Beams Using High Volume Fly Ash

2016 ◽  
Vol 3 (2) ◽  
Author(s):  
R. Thangaraj ◽  
R. Thenmozhi
Keyword(s):  
Fly Ash ◽  
Carrying Capacity ◽  
Carbon Dioxide Emissions ◽  
High Volume ◽  
Load Carrying Capacity ◽  
Environmental Friendliness ◽  
Rc Structures ◽  
High Volume Fly Ash ◽  
Load Carrying ◽  
Ultimate Load Carrying Capacity

The aim of this paper is to examine the flexural behaviour of structural beams made of high volume fly ash (HVFA) concrete with confined stirrups introduced in compression regions.Generally concrete is low tensile strength and poor ductile property. By confining compression regions introduced with closed stirrups which improves the ductility and load carrying capacity of beams. The introduction of stirrups to these regions would suppress the development of tensile stresses.Fly ash (FA) has been used in concrete and identified such a product as Eco smart or green concrete. In earth quake regions it becomes essential to construct the structures as a ductile one. Sudden failures due to poor workability of RC structures can be avoided, if critical sections are able to undergo large plastic deformations and to absorb large amount of strain energy.The results indicated that the confinement in the form of stirrups improves the ultimate strength and ductile behaviour of the concrete. It has been suggested that, the effective use of fly ash minimizes the disposal of fly ash , this HVFA concrete is easy to pump, consolidate and finish the surface, free from cracks, reduces carbon-dioxide emissions, superior environmental friendliness, reduction in stone mining since consumes less volume of Portland cement. The methodology adopted above which improves ductility, thus improving the ultimate load carrying capacity.

scholarly journals Repairing of Reactive Powder Concrete T-Beams Containing Web Opening by CFRP Strips

2019 ◽  
Vol 26 (1) ◽  
pp. 9-19
Author(s):  
Mazin B. Abdulrahman ◽  
Husham M. Rashid
Keyword(s):  
Carrying Capacity ◽  
Ultimate Load ◽  
Experimental Program ◽  
Reactive Powder Concrete ◽  
Shape Effect ◽  
Load Carrying Capacity ◽  
Test Results ◽  
Load Carrying ◽  
Ultimate Load Carrying Capacity ◽  
Reactive Powder

In modern buildings, transverse openings are often used beams for the purpose of supplying and service pipes. Due to the presence of the openings in the concrete beams lead to the formation of cracks around the openings due to the stresses concentration in a small area above and below of the opening. The repairing, maintenance, and upgrading of structural members, are maybe one of the most pivotal problems in civil engineering applications. In this research, an experimental work is conducted to study the behavior of the reinforced RPC T-beams that containing openings and repair this beams using CFRP strips. The Experimental program of the present study includes two parts, the first part includes testing of seven reinforced reactive powder concrete RPC T-beams, which casted and tested, one beam is without opening as a reference beam and the rest, were provided with an opening. and these beams are divided into two groups. The first group was used to study the effect of the openings shape (circular and square) and the second group was used to study the effect of the openings locations, which consists three locations (Lc/2, Lc/3 and Lc/4).These are measured from the support center to the openings center. While the second part including a repaired all beams in the first part the using carbon fiber polymer. The test results indicated that the presence of openings in the beams web caused a reduction in the reinforced RPC T-beams ultimate load carrying capacity with about (10-55)%, Also lead to increasing in deflection compared to control beam before repairing at same loading. Studying the shape effect showed that the beams with square openings have average ultimate load carrying capacity lower by 36% compared with the control beams.While beams with containing circular openings have average ultimate load carrying capacity lower 29%. From the test results, it could be concluded that the presence of the openings in the shear region led to a decrease in ultimate load carrying capacity a about 38% to 49% for opening of opening at (Lc/3 and Lc/4) respectively. While the presence of openings in the flexural region led to a decrease in the ultimate load carrying capacity rate of 11%. Related to the repairing study part it was found that the average ultimate load carrying capacity for repairing beams was 103% compared with the not repaired beams.

scholarly journals Multi-Step Prestressing with Hybrid SMA Wires

2020 ◽  
Vol 10 (8) ◽  
pp. 2842
Author(s):  
Chi-Young Jung ◽  
Tae-Ryeon Woo ◽  
Jong-Han Lee
Keyword(s):  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
Hydraulic Jack ◽  
Rc Structures ◽  
Prestressing Force ◽  
Rc Structure ◽  
Load Carrying ◽  
Experimental Parameters ◽  
Different Types ◽  
Prestressing Strand

Prestressing force is induced in reinforced concrete (RC) structures to improve their load-carrying capacity. Generally, the prestressing strand of an RC structure is tensioned using a hydraulic jack, which decreases its workability. In this study, we evaluate the application of prestressing force by using a shape memory alloy (SMA), as has been actively studied in civil engineering. Experiments were conducted to measure the multi-stepwise prestressing force introduced in a hybrid SMA wire composed of two different types of SMA wires. The experimental parameters were determined based on the combinations of the SMA wires and the heating temperatures. The results of the experiments show that the prestressing force was induced in a sequence. The magnitude of the prestressing force generated by the hybrid SMA wire was equal to the sum of the prestressing forces generated by the NiTi50 and NiTi90 SMA wires. In conclusion, this study verified the applicability of the proposed concept of multi-stepwise prestressing by using hybrid SMA wires. Further research is required to measure the effect of prestressing by locally heating the center of a girder with the aim of expanding the applicability of this concept.

Influence of Yield Strength Variability over Cross-Section to Steel Beam Load-Carrying Capacity

2005 ◽  
Vol 10 (2) ◽  
pp. 151-160 ◽  
Author(s):  
J. Kala ◽  
Z. Kala
Keyword(s):  
Yield Strength ◽  
Cross Section ◽  
Carrying Capacity ◽  
Bending Moment ◽  
Statistical Characteristics ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Strength Variability ◽  
Hot Rolled ◽  
Hot Rolled Steel

Authors of article analysed influence of variability of yield strength over cross-section of hot rolled steel member to its load-carrying capacity. In calculation models, the yield strength is usually taken as constant. But yield strength of a steel hot-rolled beam is generally a random quantity. Not only the whole beam but also its parts have slightly different material characteristics. According to the results of more accurate measurements, the statistical characteristics of the material taken from various cross-section points (e.g. from a web and a flange) are, however, more or less different. This variation is described by one dimensional random field. The load-carrying capacity of the beam IPE300 under bending moment at its ends with the lateral buckling influence included is analysed, nondimensional slenderness according to EC3 is λ¯ = 0.6. For this relatively low slender beam the influence of the yield strength on the load-carrying capacity is large. Also the influence of all the other imperfections as accurately as possible, the load-carrying capacity was determined by geometrically and materially nonlinear solution of very accurate FEM model by the ANSYS programme.

Fuzzy Sets Theory in Comparison with Stochastic Methods to Analyse Nonlinear Behaviour of a Steel Member under Compression

2005 ◽  
Vol 10 (1) ◽  
pp. 65-75 ◽  
Author(s):  
Z. Kala
Keyword(s):  
Fuzzy Sets ◽  
Carrying Capacity ◽  
Stochastic Methods ◽  
Nonlinear Behaviour ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Input Parameters ◽  
Stochastic Solution ◽  
Fuzzy Solution ◽  
Sets Theory

The load-carrying capacity of the member with imperfections under axial compression is analysed in the present paper. The study is divided into two parts: (i) in the first one, the input parameters are considered to be random numbers (with distribution of probability functions obtained from experimental results and/or tolerance standard), while (ii) in the other one, the input parameters are considered to be fuzzy numbers (with membership functions). The load-carrying capacity was calculated by geometrical nonlinear solution of a beam by means of the finite element method. In the case (ii), the membership function was determined by applying the fuzzy sets, whereas in the case (i), the distribution probability function of load-carrying capacity was determined. For (i) stochastic solution, the numerical simulation Monte Carlo method was applied, whereas for (ii) fuzzy solution, the method of the so-called α cuts was applied. The design load-carrying capacity was determined according to the EC3 and EN1990 standards. The results of the fuzzy, stochastic and deterministic analyses are compared in the concluding part of the paper.

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